Basis: Inhibition of transmission at receptors by acetylcholine antagonists. In the central anticholinergic syndrome, this usually involves the muscarinic receptors.
Causative agents:
(1) atropine or scopalamine associated with general anesthesia
(2) diphenhydramine or other antihistamines
(3) tricyclic antidepressants
(4) anti-parkinson medications
(5) anti-psychotic agents
(6) topical cycloplegic eyedrops
(7) herbal or plant exposure as a tea or for the hallucinogenic effect: mandrake, lobelia, burdock, thorn apple (jimson weed), Angel's trumpet
(8) antispasmodic agents for diarrhea or gastrointestinal hypermotility
(9) drugs for urinary incontinence
Presentation:
(1) psychiatric patient with agitation, dementia or coma
(2) post-operative delay in recovery or agitation, with atropine or scopalamine used in the anesthetic mix
(3) unexpected mental change in a sedated patient in the intensive care unit
(4) elderly patient on multiple medications
(5) adolescent or young adult with history of substance abuse
(6) infant or young child given atropine for head and neck surgery or through ophthalmic drops
(7) person taking large quantities of herbal teas
Central effects:
(1) dementia
(2) excitation and agitation
(3) stupor or coma
(4) hallucinations
(5) memory or thought disturbances
(6) ataxia
(7) flaccid paralysis
(8) convulsions
Peripheral:
(1) urinary retention
(2) decreased intestinal motility and constipation
(3) decreased to absent sweating, with hot and dry skin
(4) fever, with potential for severe hyperthermia
(5) decreased salivation with dry mouth
(6) dilation of pupils (mydriasis)
(7) inability to accommodate (cycloplegia), causing blurring of near vision
(8) difficulty swallowing
Therapy:
(1) Physostigmine is a cholinesterase inhibitor (decreases breakdown of acetylcholine, which increases its levels) that can pass the blood brain barrier and reverse some of the severe complications. However, it is rarely used since:
(1a) If too high a dose of physostigmine is given, or if its effects persist longer than the original intoxication, then its nicotinic effects may become pronounced and it can result in bradycardia or asystole.
(1b) It does not affect the non-cholinergic toxicities that may be present.
(2) The offending agent should be withdrawn.
(3) If agitation is present, benzodiazepines can be used to sedate the patient.
(4) If the patient is hyperthermic, then cooling should be started.
